Add In-App Search and Menu buttons support

[PetbkA]

Description

Long time ago there were:

1. In-app Search (key code 84)
2. And Menu (key code 82)

buttons in Android navigation bar.

They've been replaced by Home and Recent Apps, but are still supported in Android (checked with KeyEvent Display and can be triggered via the navbar in distributions like LineageOS (see a screenshot).

Is it possible to add their support in Auxio, i.e.:

1. In-app Search will trigger Search;
2. Menu will trigger More options/three-dots-menu

?

Problem solved

No response

Other implementations

Black Player EX recognizes both key events as In-App Search

Benefit

This can solve couple of problems:

1. No need to reach for UI buttons on top of the screen;
2. They can be called from playback screen and other places where they're absent.
   For Menu it won't look pretty in latter cases (option list would appear out of nowhere) but Search will be OK as it has separate screen

Duplicates

• I have checked this feature request for duplicates.
• I have checked that this feature is not implemented in the lastest version.
• I have checked the Why Are These Features Missing? page.
• I agree to the Contribution Guidelines.

[OxygenCobalt]

I don't see the use for this to be honest. It feels very much like legacy cruft. Keeping it open in the case of demand.